The Aerogeophysical Atlas of Tocantins State: Synthesis of Magnetic Anomaly And Radioelement Maps With Emphasis on Regional Signatures and the Serra Da Cangalha Impact Structure

Adolfo Barbosa da Silva, Marcelo Ferreira da Silva, Wolf Uwe Reimold, Felipe da Mota Alves, Alexandre Lisboa Lago, Marco Antônio Couto Jr, Antônio Augusto Soares Frasca, Pedro Sérgio Estevam Ribeiro

Abstract


The Tocantins State Aerogeophysical Atlas (TSAA) is an institutional product of the Geological Survey of Brazil. It is aimed at promoting the use of airborne magnetic and gamma-ray spectrometry data to support geophysical and geological research at state level. Here, we present a synthesis of the TSAA with special emphasis on the interpretation of the magnetic (Anomalous Magnetic Field, First Vertical Derivative (FVD), and Total Gradient Amplitude (TGA) images) and radiometric (RGB composite color map of concentrations, Inverse Images of K, eTh, and eU, and Normalized eU enhancement) map. In particular, the radiometric data for the Serra da Cangalha impact structure in northeast Tocantins are discussed. For Tocantins State, the results show that the radiometric and/or magnetic signatures of geological units (e.g., Mosquito Formation basalts; granite-gneiss/migmatite terrains) and structural features (e.g., dykes and lineaments), or related exogenous deposits (Serra Geral do Tocantins quartzose soils; alluvial deposits of main drainage channels) can be visualized well on regional-scale maps. Analysis of radiometric ratios for the area of the Serra da Cangalha impact structure indicates that eU concentrations are enriched in the annular basin around the central uplift structure, and in the zone straddling the contact between the Piauí and Pedra de Fogo formations. In the latter case, the elevated eU concentrations could be related to brecciated chert layers or silicified sandstones.


Keywords


Tocantins state aerogeophysical data; gamma-ray spectrometry; magnetometry; geological-geophysical integration; Serra da Cangalha impact structure

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DOI: http://dx.doi.org/10.22564/brjg.v42i2.2316

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